Lubricant with high temperature stability



Patented Aug. 18, 1942 LUBRICANT WITH HIGH TEMPERATUR STABILITY Joseph F. Nelson, Elizabeth, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Appl cation November 19, 1938, Serial No. 241,333

1 Claim.

The present invention relates to the art of lubrication and more specifically to lubricants with high temperature stability such as to make them desirable for use in automotive engine lubrication and otherwise where high temperature stability is required. The invention will be understood from the following description:

Mineral lubricating oils have been widely used as lubricants for many years, but within the last few years the severity of the conditions under which they are used has so greatly increased that in many cases unblended oils have proved to be lacking in certain properties and recourse has been had to improvement by the addition of blending agents to increase one or more desirable properties. The great majority of types of blending agents, however, have not been wholly satisfactory because while they may improve one particular property of the oil, they may equally well decrease its effectiveness in some other respect. Such agents as have been used are generally employed in specific types of equipment and there are no generally universal agents, which are good for all or even a majority of the conditions likely to be met.

Agents have now been found, however, which come closer to the ideal than any yet proposed in that they make an improvement in almost all of the desired properties of an oil for the lubrication of automotive engines. Thus in an engine oil, the lubricant is preferably highly refined and this in itself ordinarily makes it more sensitive to oxidation and decomposition. To

be satisfactory the oil should have a low oxidat.'on rate. It should. be capable of carrying higher loads than the unblended oils, and give a clean engine especially in respect to piston rings, ring grooves and the like. It must also minimize or reduce deposition of carbon and the varnish like deposits which are frequently found in engines.

The agents which have been found most satisfactory according to the present invention fall within the class of aromatic phosphite or thio phcsphite esters which contain substituent hydrorryl, or mercapto groups or modified hydroxyl or mercapto groups, i. e., esterifled or etherified. Among the various compounds, those containing a hydroxyl group directly attached to the aromatic are preferred. The aromatic may be of the single ring type as found in phenol, cresol or diphenyl, or may be of the condensed ring type such as found in naphthols .or anthrols.

or thio phenolic compounds ar preferable to the unalkylated products of all types.

Of the numerous compounds, the phosphite esters of polyhydroxy phenolic compounds, in which at least one of the hydroxyl groups is unesterifled, are found to be very excellent, for example ortho, meta or para-hydroxy phenyl phosphite, or the alkylated derivatives corresponding to the cresol compounds, or those with higher alkyl groups such as ethyl, the various propyl, butyl, amyl or higher alkyl groups. These alkylated hydroxy phosphites are preferable to the unalkylated products.

As stated before, the hydroxyl or mercapto groups may be modified by chemical reaction. The most general chemical formula might be where R is a hydrocarbon radical either alkyl or aryl, X is an O or S atom, Y is an 0 or S atom,

or alcohol. More specific formulae, such as the following will be more-helpful:

(Q-Y i? SH 3 {all 3 ill! radicals are on the aromatic radical, but these expressed as follows:

and R is a hydrogen atom or a residue of an acid (Q s- (QT 0H s H 3 SH 0- P R sare hydrocarbon radicals,

It is usually the case that the alkylated phenolic oxidation of paraffin wax at low temperatures,

but acetic acids may also be used. In the same manner the alkyl groups either attached directly to the aromatic ring or on the ether may be short chain, for example, ethyl, methyl, propyl, or butyl, or they may be higher molecular weight radicals such as cetyl, lauml, oleyl, octa'decyl, and the like, but phenolic radicals may likewise be used.

The materials described above are added to was measured and absorption was estimated by difference. The oxidation rate of the blank sample was found to be 82--60-48 cc. of oxygen per 15 minute intervals, while the sample containing the addition agent showed a rate of 34-57.

EXAMPLE II To another sample of a similar oil S. A. E. grade 40, 911% of tritertiary butyl ortho hydroxy mineral lubricating oils in proportion of from .1 phenyl phosphite was added and engine tests to about 1 or 2% by weight. They may also be were made in a C. F. R. engine for a period of employed as the sole addition agents because 14 hours on each of the samples. they have excellent properties not onlyof oiliness The engines were run under carefully conbut also for reducing oxidation, preventing ring trolled and comparable conditions and after each sticking, reducing carbon deposition and the like, 15 test the pistons were taken down and examined. and they may be used in conjunction with other A rate was assigned to each part depending on materials to further enhance these properties, its condition and the amount of the carbon and for example additional oxidation inhibitors of varnish, the number of rings stuck and the deother types, sludge dispersers, pour inhibitors, gree of sticking were noted. All of this data perand the like. They may be used also in connec- 20 mits a clear comparison of the engine when using tion with metallic soaps, particularly those of the two different oils and an overall rating is obaluminum, calcium, nickel, chromium, and the tained in which weight is given to each of the like, for the particular purpose for which these individual portions of the engine. It will be rematerials are ordinarily used. The lubricating membered that in all cases the lower numbers il m y be f y desired p useful r0 the p r- :5 indicate the better engine condition. ticular purpose at hand, derived either from the The data is given in the following table:

C. F. R. ENGINE PERFORMANCE Demerits Percent Piston Rings Degree Ring Ring 9 2 3 2, Varnish Carbon reference overall stuck sticking slits grooves piston skirt formed Blank oil 100 4.10 3 810 2.83 6.00 4 4.5 4.67 Ditto+%% tritert.-bu-

tyl-o-hydroxyphenyl phosphite 22 0.97 0 o 0.11 2.25 1.5 0.5 1.24

paraflinic, asphaltic or naphthenic crudes, and The thio-pheriolic or thio-phosphite compounds the viscosity is chosen for the particular purare found to give equally good results. pose. 40 From the above data it is clearly apparent The following examples of the present comthat the addition agent has greatly improved the pounds may be considered illustrative of the inoperation of the oil in the engine. vention: The present invention is not to be limited by EXAMPLE I any theory of the mechanism by which the ad- To a hydrocarbon lubricating on E. 20 was dition agent efiects the improvement nor to any added /47 of a tmert but 1 ortho h dmx particular addition agent, but only to the foly y y lowing claim in which it is desired to claim all phenyl phosphite. The oxidation rates of the oil novelty inherent in the invention and the oil to which this compound was added I claim: were then determined by passing a major volume 5 A composition comprising a highly fi ed of oxygen in a closed system so as to bubble through a 10 cc. sample which was held at 200 C. At 15 minute intervals the volume of the gas mineral oil and tritertiary butyl ortho hydroxy phenyl phosphite.

JOSEPH F. NELSON. 

